Older MCQs might not have the typical A, B, C,
D
choices. They
have choices 1, 2, 3, and a combination of them is the answer. Below is the key that maps such
combinations to the answer.
A
1, 2 and 3 are correct
B
1 and 2 only are correct
C
2 and 3 only are correct
D
1 only is correct
recall the reactions (reagents and conditions) by which halogenoalkanes can be produced: (a) the free-radical substitution of alkanes by \( Cl_2 \) or \( Br_2 \) in the presence of ultraviolet light, as exemplified by the reactions of ethane (b) electrophilic addition of an alkene with a halogen, \( X_2 \), or hydrogen halide, \( HX(g) \), at room temperature (c) substitution of an alcohol, e.g. by reaction with \( HX(g) \); or with KCl and concentrated \( H_2SO_4 \) or concentrated \( H_3PO_4 \); or with \( PCl_3 \) and heat; or with \( PCl_5 \); or with \( SOCI_2 \)
describe: (a) the complete and incomplete combustion of alkanes (b) the free-radical substitution of alkanes by \( Cl_2 \) or \( Br_2 \) in the presence of ultraviolet light, as exemplified by the reactions of ethane
describe and interpret, in terms of changes in oxidation number, the reaction of chlorine with cold and with hot aqueous sodium hydroxide and recognise these as disproportionation reactions
